Column name for inline explode

[linhr]

This is the behavior for JVM Spark:

>>> spark.sql("""SELECT inline(array(struct(1), struct(2)))""").show()
+----+
|col1|
+----+
|   1|
|   2|
+----+

>>> spark.sql("""SELECT inline(array(struct(1, 'a'), struct(2, 'b')))""").show()
+----+----+
|col1|col2|
+----+----+
|   1|   a|
|   2|   b|
+----+----+

This is the behavior for Sail currently:

>>> spark.sql("""SELECT inline(array(struct(1), struct(2)))""").show()
+-----------------------------------+
|inline(array(struct(1), struct(2)))|
+-----------------------------------+
|                                  1|
|                                  2|
+-----------------------------------+

>>> spark.sql("""SELECT inline(array(struct(1, 'a'), struct(2, 'b')))""").show()
+----+----+
|col1|col2|
+----+----+
|   1|   a|
|   2|   b|
+----+----+

So the inner field name is not preserved when the struct has only one field. This should be fixed.